Panda3D provides a safe threading interface you can use, which works very similar to Python’s threading modules. Panda3D is compiled by default to use “true” threading, which makes it safe to use Python threading interfaces (or any other threading library) in conjunction with or in lieu of Panda’s own built-in threading interfaces described below.
If you want to test whether threading is enabled in your build of panda, use the following program:
from panda3d.core import Thread print(Thread.isThreadingSupported())
If threading is enabled, it’s also possible to turn it off, for example if you want to test if a certain problem you are experiencing is related to threading. Put this in your Config.prc:
Panda3D provides several useful high-level functions for loading models and doing other expensive operations in a thread, so the user of your application will not notice chugs in the frame rate. These functions are managed by Panda3D automatically, so do not require knowledge of threading. It is recommended that you first seek out these features before implementing threading yourself.
See Asynchronous Loading for more information about these features.
If you want to use threading with Panda3D, it’s not recommended to use Python’s built-in threading modules, since you will most likely run into issues (for Panda3D is written in C++ and thus does not use the Python threading modules). However, Panda3D offers a threading implementation that is safe to use, by reimplementing Python’s “thread” and “threading” modules, these work the same as the Python built-in threading modules but are actually safe to use with Panda3D.
# WRONG: import thread # RIGHT: from direct.stdpy import thread
For the Python module
threading, Panda3D offers two equivalents,
you can find both in
threading module implements the threading module
with a thin layer over Panda’s threading constructs. As such, the semantics are
close to, but not precisely, the semantics documented for Python’s standard
threading module. If you really do require strict adherence to Python’s
semantics, see the
threading2 module instead.
In fact, the
threading2 module is a bald-face copy of
threading module from Python 2.5, with a few lines at the top
to import Panda’s thread reimplementation instead of the system thread module,
and so it is therefore layered on top of Panda’s thread implementation.
However, if you don’t need such strict adherence to Python’s original semantics, the “threading” module is probably a better choice. It is likely to be slightly faster than the threading2 module (and even slightly faster than Python’s own threading module). It is also better integrated with Panda’s threads, so that Panda’s thread debug mechanisms will be easier to use and understand.
# WRONG: import threading # RIGHT: from direct.stdpy import threading # ALSO RIGHT: from direct.stdpy import threading2 as threading
It is permissible to mix-and-match both threading and threading2 within the same application.
Panda3D also offers a thread-safe replacement for the Python file module. You
can find it in
direct.stdpy.file. The interface is exactly the same as
Python’s, so it’s safe to put this import above all the files where you want to
from direct.stdpy.file import *
This module reimplements Python’s file I/O mechanisms using Panda constructs. This enables Python to interface more easily with Panda’s virtual file system, and it also better-supports Panda’s SIMPLE_THREADS model, by avoiding blocking all threads while waiting for I/O to complete.
Compiling Panda3D with threading support
There are two different interfaces for threading which you can enable using the definitions HAVE_THREADS and SIMPLE_THREADS. The former is a full and heavy implementation of threading and compiling with that option will slow down the Panda3D build, unless you fully make use of the benefits that threading gives. The latter, however, is a more simple threading interface that doesn’t give you the runtime overhead HAVE_THREADS gives you.
Note that you will have to define both HAVE_THREADS and SIMPLE_THREADS at the same time to enable the simple interface, or you will not have threading.
The public builds enable true threading by default, so you will not need to build Panda3D yourself if you want to take advantage of true threading.
If you wish to disable threading, you can pass the option
--override HAVE_THREADS=UNDEF to makepanda.py. If you wish to use the simple
threading model, you may pass
--override SIMPLE_THREADS=1 instead.